1. Field of the Invention
The present invention relates to an artificial tooth crown made of glass ceramics (recrystalized glass), i.e., calcium phosphate-based minerals forming essentially apatite, and a method of producing the artificial tooth crown.
2. Prior Art
The conventional artificial tooth (hereinafter, refer to merely as "crown") crowns are classified into four types. The first type is made of metal, the second type is made of porcelain (jacket crown), the third type is made of a combination of metal and porcelain (metal bond) and the fourth type is made of a combination of metal and resin. The crown of the first type made of precious metal, semi-precious metal or nonprecious metal can have a highly precise shape by precision casting. However, the crown made of precious or semi-precious metal is expensive and the luster inherent in such metal does not match well with the living body and is disliked. In the case of the crown made of nonprecious metal, the harm of nonprecious metal to the living body has been reduced considerably by the improvement of metal qualities but has not yet been completely eliminated. The second type is produced by a repeatedly building and firing porcelain. Therefore, the dimensions of the crown produced in this way may be changed by repeated heat application, thus it may not properly fit to natural teeth. Accordingly, the yield rate of this type is extremely low since it needs high technology of porcelain building and firing and must have high dimensional accuracy, resulting in high production cost.
In the case of the third type made of a combination of metal and porcelain, porcelain is built and baked on the crown surface to shade the luster of the matal crown. In this case, the problems regarding the first type will also arise, and its production is complicated and requires high cost. Furthermore, the metal crown is not harder than the opposed natural tooth and thus it is locally corroded or deformed by biting motion for an extended period. On the contrary, the crown made of or coated with porcelain is harder than the natural tooth and wears out the opposed natural tooth. In addition, dimensional accuracy drops due to repeated heat treatment as described above. The fourth type made of a combination of metal and resin is apt to discolor and fatigue easily. That is, the fourth type is not durable due to deterioration after use for an extended period.